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(CNN)On Monday at his daily briefing, White House press secretary Sean Spicer was asked whether it was safe to assume President Trump would never release his tax returns.

"We'll have to get back to you on that," Spicer said.

Riiiiiight. I won't hold my breath.

Since we aren't likely to learn much from Team Trump about his tax returns, I figured I'd dig deep and see what I think I know about them. (I say "I think" because I've learned with Trump that you never know even what you think you know.)

First, here's my list of what I know:

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1. In 1978 and 1979, Trump reported negative $3.8 million in income and paid no taxes. We know that because of a 1981 gambling commission report in New Jersey that details Trump's income (or lack thereof) as reported in a casino application around that time.

2. In 1995, Trump reported that he lost $916 million -- an amount that could have allowed him not to pay taxes for nearly the next two decades, according to the New York Times.

4. His most recent returns are under audit, according to the White House. Spicer affirmed that fact on Monday. (Note: You can release your taxes publicly even if you are under audit. Richard Nixon did.)

And that's it.

Now, to the more speculative/educated guesses portion of this post. Here's what I think I know about Trump's tax returns.

1. Trump won't release them. Ever. From Trump's point of view, why would he? Hillary Clinton made Trump's tax returns and lack of transparency a major focus of her 2016 campaign, and he still won. Voluntarily releasing at this point is just not in the cards. The only way I can see Trump putting out the returns is if they are the only thing that can prove his lack of culpability in the Russia hacking scandal. And we're not even close to there yet.

2. People say they care about Trump's taxes.But they don't vote on them. Most polls I've seen show somewhere between 55 and 65 percent of people think the President should release at least some of his taxes. Two Republicans -- Reps. Mark Sanford (South Carolina) and Walter Jones Jr. (North Carolina) -- have signed on to a letter urging the relevant congressional committees to obtain copies of Trump's returns. The problem for people who want to see Trump's tax returns is that outside of the core Democratic base -- not exactly Trump's target audience -- people just don't cast their votes on the issue. If they did, Trump would have lost last November.

3. Trump made a calculation a long time ago that what's in the returns is worse for him politically than not releasing them. During the campaign, Trump used to say that no lawyer would advise any client to release their returns while under audit. OK. But those clients aren't running for or serving as the President of the United States. The audit, therefore, has always felt like a veil hiding the real reason Trump didn't want to release the returns: Because they showed a) he wasn't as rich as he said, b) he didn't pay much in taxes, c) the the documents revealed some sort of blatant conflict of interest, or d) some other reason I haven't thought of.

And here's one other thing I know: In refusing to release his tax returns, Donald Trump is the least transparent presidential candidate -- and President -- in at least four decades. And I also know this: He doesn't care at all.